1. Field of the Invention
The present invention is generally related to switches with deformable membranes formed as part of the switch housing and, more particularly, to a switch which incorporates a laminated cover with a central sheet disposed between two plates, wherein the central sheet is shaped to define a raised deformable membrane extending through an opening in one of the plates and aligned with an opening in the other plate.
2. Description of the Prior Art
Hermetically sealed switches which incorporate a deformable membrane as part of the switch housing are known to those skilled in the art and are commercially available from MICRO SWITCH, A Division of Honeywell, as identified by Catalog Listing HM. As will be described in greater detail below in conjunction with FIGS. 1 and 2, the known way to manufacture a hermetically sealed switch of this type is to form a cover plate with an opening therethrough and separately form a cup-shaped member having a generally circular deformable membrane as a surface thereof. The cup-shaped member is then inserted through the opening in the cover plate and an annular rim of the cup-shaped member is brazed to the plate around the edge of the opening in the plate. A pin is brazed into a hole in the center of the cup shaped member. External and internal levers are attached to the pin in the deformable membrane to permit actuation of a switching mechanism by the internal lever in response to movement of the external lever. Although this particular design of switch has worked satisfactorily for many years, the connection between the cup-shaped member and the cover plate is subject to significant process variability during manufacture. This process variability can reduce the corrosion resistance of the switch, adversely affect its mechanical life or lead to sealing failures. It would therefore be beneficial if a switch of this general type could be made in a way that reduces or eliminates the variability of the manufacturing process which can result in failures in the region where the cup-shaped member is brazed to the cover plate.